Shallow-water blackout

Loss of consciousness at a shallow depth during a dive

Shallow-water blackout is loss of consciousness at a shallow depth due to hypoxia during a dive, which could be the result of any one of significantly differing causative circumstances. The term is ambiguous, and the depth range in which it may occur is generally shallow relative to the preceding part of the dive, but also occurring when the entire dive takes place at an almost constant depth within a few metres of the surface. Various situations may be referred to as shallow water blackout but differ in how the hypoxia is induced: Some occur in a context of freediving, others occur during ascent while scuba diving, usually when using a rebreather, and occasionally while surface-supplied diving.

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